When accessing the Needs Checklist task from the onBoard Dashboard, I find that several of the Candidates will not process. When I add the checklist and click the process button, the user returns right back to the needs checklist area.
Make sure that the first Checklist step is an Entering Milestone. If not, no status can be applied to the Candidate and they will continue to return to Needs Checklist.
To change the checklist milestone:
onBoard > Settings
Edit the Checklist
Click the Pencil Icon to the right of the first Milestone